The present invention relates to reciprocating and hermetic compressors applicable to refrigerating systems and others.
One of the major problems arising in the use of hermetic compressors is occurrence of noises and vibrations. Recently, improvement for such hermetic compressors is being made for the noise- and vibration-reduction purposes. One known noise and vibration reduction technique is disclosed in the Japanese Utility Model Publication No. 49-18245 where a compressing unit is elastically supported by springs with respect to a closed vessel. This prior art technique will be described hereinbelow with reference to FIG. 1 which is a cross-sectional view showing a conventional hermetic compressor. In FIG. 1, designated at numeral 1 is a hermetic compressor which is equipped with a compressing unit comprising a compressing section 5 and a motor section 6 which are encased in a closed vessel 4 Comprising an upper shell 2 and a lower shell 3. The compressing section 5 is constructed with a cylinder 9 formed in a block 8, a piston 10 associated with the cylinder 9, a crank shaft 11 having a crank eccentric portion (crank pin) 11a, a con'rod 12 coupled to the crank shaft 11, and a bearing 13 provided on the block 8 to support the crank shaft 11. Further, the motor section 6 is constructed with a rotor 14 and stator 15, the rotor 14 being fixedly shrinkage-fitted to the crank shaft 11 and the stator 15 being fixedly secured through screws to the block 8. In addition, on a lower end portion of the stator 15 there is provided a spring-mounting plate 17 having studs 16. Springs 7 are placed between the studs 16 and the lower shell 3 so as to elastically support the compressing section 5 and the motor section 6.
With this arrangement, when vibrations of the compressing unit occur in response to the refrigerant-compressing operation of this compressor, the springs 7 can attenuate the vibrations before the propagation to the closed vessel 4 to thereby suppress the occurrence of noises due to the vibration of the closed vessel 4.
There is a problem which arises with such a conventional compressor arrangement, however, in that a moment can be generated and applied to the crank shaft 11 due to the balance configuration of the compressing unit relative to the supporting position and hence difficulty is actually encountered to sufficiently suppress the vibration of the closed vessel.
Further, the Japanese Patent Publication No. 58-24633 discloses a technique in which a balance weight is provided at the vicinity of the crank eccentric portion 11a of the crank shaft 11. However, this arrangement cannot also sufficiently suppress the generation of the moment in the crank shaft 11.